Positioning pivots are commonly used in many casing structures such as notebook computers. As shown in FIG. 5, a conventional positioning pivot comprises a shaft (90) having a first portion (92) with at least one first through holes (93) to connect with an object and a second portion (94) with a helical groove (96) defined on the surface. A hinge butt (80) includes at least one collar (82) and an extension (84) integrally formed therewith. The extension (84) of the hinge butt (80) has at least one second through hole (86) defined therein. The second portion (94) of the shaft (90) is rotatably received within the collar (82) of the hinge butt (80), after the first through hole (93) is securely connected to an object, such as a screen (not shown), and the second through hole (86) of the extension (84) is securely connected to a computer (not shown). The positioning pivot of this type can indeed provide a pivot effect to the objects which the positioning pivot connects with. However, the friction between the second portion (94) of the shaft (90) and the collar (82) will gradually enlarge the clearance therebetween and thus causes a loose connection. In order to mitigate the above mentioned problem, a helical lubrication groove (96) is defined in the outer periphery of the second portion (94) of the shaft (90) and lubricant (not shown) will thus be spread from the lubrication groove (96) to the surface of the second portion (94). Therefore, the friction between the second portion (94) of the shaft (90) and the collar (82) of the hinge butt (80) is greatly reduced after the second portion (94) is inserted into the collar (82).
Nevertheless, the lubricant spread onto the surface of the second portion (94) of the shaft (90) can only lubricate part thereof because the rotation between the collar (82) and the second portion (94) is limited within a certain arc of rotation.
To enhance the lubrication effect between the second portion (94) and the collar (82), as shown in FIG. 6, a new type of positioning pivot is introduced.
The positioning pivot also has a shaft (90) with a first portion (92) that has at least one first through hole (93) for connecting the positioning pivot to an object, such as a screen (not shown), and a second portion (94) with a helical lubrication groove (96) defined in the surface. The positioning pivot further has at least one sleeve (70) having at least one protrusion (72) formed on an outer peripheral wall thereof, a helical slit (73) defined therein and a hinge butt (80A) having at least one collar (82) provided with at least one cutout (83) defined to correspond to the at least one protrusion (72) and an extension (84) integrally formed therewith and provided with at least one second through hole (86) for connecting with an object, such as a computer (not shown). The helical slit (73) of the sleeve (70) is oriented opposite to the orientation of the helical groove (96) of the second portion (94) of the shaft (90), such that lubricant in the helical groove (96) of the second portion (94) is able to be dispersed to a larger portion when the shaft (90) is rotated manually by a user. Accordingly, after the sleeve (70) is inserted into the hinge butt (80A) to have the at least one protrusion (72) received in the cutout (83) and securely retained therein, there will be no relative movement between the collar (82) and the sleeve (70), but between the sleeve (70) and the second portion (94) of the shaft (90). After assembly, the lubrication effect of the structure as shown in FIG. 5 is not satisfied, however, the lubrication effect of the structure as shown in FIG. 6 provides a smooth pivot between the shaft (90) and the hinge butt (80A). However, the structure as shown in FIG. 6 provides more lubrication than necessary, such that the screen may fall to the computer base during operation. In order to provide a positioning pivot, which is able to provide a moderate lubrication effect, alternation or modification to the present structure is necessary.
From the previous description, it is noted that a positioning pivot as described above is not able to fulfill the practical requirements.
Thus, a positioning pivot constructed in accordance with the present invention tends to mitigate and/or obviate the aforementioned problems.